#include<bits/stdc++.h>
#define For(i, x, y) for (int i = x, i##end = y; i <= iend; ++i)
using namespace std;
constexpr int _N = 3e5 + 5;
int n, m, pre[_N], nxt[_N];
unordered_set<long long> H;
void Ins(int x, int y) { H.insert(1ll * x * _N + y); }
bool Chk(int x, int y) { return H.count(1ll * x * _N + y); }
void Add(int x, int y, int i) { pre[y] = i, nxt[x] = i, pre[i] = x, nxt[i] = y; }
signed main() {
   ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
   cin >> n >> m;
   For(i, 1, n) {
      int x, y;
      cin >> x >> y, Ins(x, y), Ins(y, x);
   }
   int p = 2;
   pre[0] = 2, pre[1] = 0, pre[2] = 1;
   nxt[0] = 1, nxt[1] = 2, nxt[2] = 0;
   For(i, 3, n) if (p == 1) {
      p = pre[0]; Add(p, nxt[p], i);
      if (Chk(p, pre[p]) == Chk(p, nxt[p])) p = 1;
   } else if (Chk(p, i) == Chk(p, pre[p])) {
      Add(p, nxt[p], i);
      if (nxt[i] && Chk(i, pre[i]) == Chk(i, nxt[i])) p = nxt[i];
      else p = i;
   } else {
      Add(pre[p], p, i);
      if (pre[i] && Chk(i, pre[i]) == Chk(i, nxt[i])) p = pre[i];
      else p = i;
   }
   for (int i = nxt[0]; i; i = nxt[i]) cout << i << ' ';
   cout << '\n';
}